1. Field of the Invention
The invention is directed to an improved fuel injection valve for internal combustion engines, preferably internal combustion engines with self ignition.
2. Description of the Prior Art
In one known fuel injection valve, disclosed in German Utility Model 298 14 934, a bore is embodied in a valve body, and in the bore a pistonlike valve member is disposed longitudinally displaceably; by its longitudinal motion, the valve member controls the opening of at least one injection opening. The valve member is urged in the closing direction by a closing force and has a pressure face, which is disposed in a pressure chamber that can be filled with high fuel pressure. Filling the pressure chamber with fuel at high pressure makes it possible to exert a hydraulic force on the pressure face that is oriented counter to the closing force and thus brings about the opening stroke motion of the valve member. The device for generating the closing force is embodied in a valve holding body, which has a longitudinal axis and is braced axially against the valve body. A high-pressure connection is located on the valve holding body and discharges into an inlet conduit that penetrates the valve holding body longitudinally and extends through the contact face between the valve body and the valve holding body as far as the inside of the pressure chamber of the valve body. The contact face is accordingly a high-pressure sealing face and must have a correspondingly good seal.
The bracing of the valve holding body against the valve body if effected by a lock nut, which surrounds the valve body and contacts an annular-disklike contact face, embodied on the valve body, that faces away from the valve holding body. On the valve holding body, there is a male thread engaged by the lock nut with a corresponding female thread, so that the valve body is braced against the valve holding body by the screwing action of the lock nut. As a result, a good seal is achieved at the high-pressure sealing face between the valve holding body and the valve body, and the inlet conduit that passes through the high-pressure sealing face, that is, the contact face of the valve holding body at the valve body, is securely sealed off.
In the known fuel injection valves, the thread, embodied on the outer jacket face of the valve holding body and engaged by the lock nut, is embodied as a fine thread. The flanks of the thread courses form an angle of about 60xc2x0 with the longitudinal axis of the thread and thus also with the longitudinal axis of the valve holding body. Thus because of the axial bracing of the lock nut, along with the axially operative force component on the screw faces, a force component acting in the radial direction to the longitudinal axis of the valve holding body is also obtained, which expands the lock nut. This limits the maximum attainable pressure per unit of surface area at the high-pressure sealing face between the valve holding body and the valve body, so that at high pressures in the inlet conduit, sealing problems can occur.
The fuel injection valve of the invention has the advantage over the prior art that the contact flanks of the male thread embodied on the valve holding body and of the female thread embodied on the lock nut are at least approximately perpendicular to the longitudinal axis of the valve holding body, so that upon the bracing of the lock nut, these contact flanks are pressed against one another without substantial radial forces on the lock nut being engendered. As a result, greater axial clamping forces can be exerted on the valve body and the valve holding body, and a higher pressure per unit of surface area can thus be achieved at the high-pressure sealing face between the two bodies. Expansion of the lock nut from radial force components thus no longer occurs. This is especially advantageous in fuel injection valves that work with a so-called common rail system, because in that case a constantly high fuel pressure prevails in the valve body.